The present invention relates to electrical engineering, in particular to a lamp holder and more particularly to a tubular fluorescent lamp holder according to the preamble of claim 1. The two most common fluorescent lamp holder assemblies for by-pin fluorescent lamps are the so-called “twisted type” and “spring type”.
In the “twisted type” lamp holder assembly shown in FIG. 1, during the installation of the lamp, the pins at both ends of the fluorescent lamp must first be introduced into radial grooves in the lamp holder adapted to receive these pins and then the lamp must be twisted about 90 degrees around its longitudinal axis to complete the installation.
In the “spring type” lamp holder assembly shown in FIG. 2, during installation of a lamp, the pins on one end of the lamp are inserted first into a pin dock of the lamp holder provided with a spring. Then, the spring must be pressed inwards, and afterwards the other end follows the same way. The exertion of the springs on each end of the lamp holds the lamp in place.
In both types of fluorescent lamp holder assemblies, the installation or replacement of the lamp requires a certain skill and it becomes especially difficult when these operations must be done at a certain height, for example at the top of a ladder.
In order to overcome these problems, lamp holder assemblies comprising a socket and a connectable lamp holder have been suggested. In detail, a socket is fixed to the lighting fixture, one at each end, and electrically connected to an electrical source. The socket comprises two electrical terminals defining insertion inlets for the corresponding legs of the holder. On the other hand, the holder comprises two legs electrically connectable to the pins of the fluorescent lamp and adapted for connection in the insertion inlets of the socket. During the installation, first the pins of each fluorescent lamp ends are inserted into the corresponding holder terminals. Afterwards, this subassembly is connected to the fixture by inserting the legs of each holder into the insertion inlets of its corresponding socket in a direction normal to the fluorescent lamp's axis. However, this solution has the problem, that the holder can loosen from the socket and thus the fluorescent lamp can fall down.
In order to overcome this problem, document U.S. Pat. No. 2,449,736 discloses a lamp holder assembly of the type described above, in which the holder is provided with protruding spring type latching legs which can be deflected towards each other by means of finger grips pivoted to the body of the holder. The free end of these parallel legs also has outwardly projecting prongs. When the holder is plugged into the socket, converging slopes provided within the housing of the socket deflect the prongs, and thus the legs, toward each other. Once the prongs have surpassed these slopes, the legs snap back to their original position and establish an electrical contact with the corresponding electrical terminals in the socket. Furthermore, the prongs prevent the holder from being pulled out of the socket. This solution has the drawback that less pressure can be exerted between the terminals of the socket and the holder and therefore a less reliable electrical contact can be achieved. Furthermore, if a user tries to replace the lamp by pulling the socket without disengaging the outwardly projecting prongs pressing on the finger grips, the legs and thus the electrical contact between the terminals can seriously be damaged.
Document GB 630,143 discloses securing means between the socket and the holder. The holder is secured to the socket by passing a pin through an aperture in the holder, into the socket until the grooves provided at the end of the pin are received and held in spring members provided in the socket. When the pin is rotated 90 degrees around its axis, the grooves are disengaged from the spring means and thus, the holder can be removed from the socket. This system is quite complicated and since the pin is rather small, it is not easy to handle.
Document U.S. Pat. No. 2,231,851 also discloses securing means between the socket and the holder of a fluorescent lamp holder assembly. In this case, the blade or flat type terminals of the holder are provided with protuberances adapted to snap into corresponding recesses in the socket terminals. This solution unnecessarily increases the plugging and unplugging force needed to assemble and disassemble the holder and can hinder installing or replacing the fluorescent lamp.
Document U.S. Pat. No. 2,511,155 discloses securing means between the holder and the socket via the fluorescent lamp. To this end, the lighting fixture is provided with spring clips located on the underside of the lighting fixture and between the lamp holders. The spring clips are arranged to resiliently hold the metallic sleeves supporting the connection pins at each end of the fluorescent lamp. One of the drawbacks of this solution is that when plugging or unplugging the holder, an additional force is exerted on the pins of the fluorescent lamp which can eventually lead to pin damage if both holders are misaligned during the plugging or unplugging process.
Document JP 3291803A discloses a lamp socket providing a contact piece which can be removably engaged with a lamp socket mounting base and is to be connected to a joint piece at the time of mounting it onto the mounting base. In assembling the lighting fixture, a fitting part 15 of a lamp socket 12 is fitted into a fitting recess 8 of a lamp socket mounting base 4, a protrusion 16 is fitted into a recessed stage 9 while a contact piece 17 of the protrusion 16 is brought into contact with the contact piece 10 of the recessed stage 9 to have them electrically connected to each other. An elastic hook piece 18 provided on the rear of the protrusion 16 is engaged with an engaging locking hole 11 formed on the recessed stage 9 at this time, wherein the lamp socket 12 is engaged and held by the lamp socket mounting base 4. When the lamp socket 12 is to be removed from the mounting base 14, by pushing the elastic hook piece 18 provided on the rear of the protrusion 16, engagement between the elastic hook piece 18 and the engaging locking hole 11 is released so that the lamp socket 12 can be removed from the mounting base 4.
Therefore, it is an object of the present invention to provide an alternative fluorescent lamp holder assembly wherein installation or replacement of a fluorescent lamp can be done conveniently and easily and preventing the user from having to exert unnecessary plugging or unplugging forces.